Microwave modulating attenuator roll stabilization system



1961 H. H. GEORGE 2,997,255

MICROWAVE MODULATING ATTENUATOR ROLL STABILIZATION SYSTEM Filed Jan. 14, 1955 3 Sheets-Sheet 1 FIG.

2 MIIIXER 24 7 v as 22 25 RECEIVER |I PH ASE COMPARATOR BIAS VOLTAGE 54 SUPPLY RC LL 33 STABILIZATION SERVO SYSTEM INVENTOR. HE NR) h. GEORGE BY 1X10. Q/ZW ATTORNEYS Aug. 22, 1961 H. H. GEORGE 2, 7,

MICROWAVE MODULATING ATTENUATOR ROLL STABILIZATION SYSTEM 3 Sheets-Sheet 2 Filed Jan. 14, 1955 STABILIZATION SERVO SYSTEM SUMMED SIGNAL HORIZONTAL COMPONENTS REMOVED BY THE HORIZONTAL STRIP OUTPUT SIGNAL RECEIVED BY CRYSTAL DETECTOR FIG. 5

b INVENTOR.

HENRY H. GEORGE (Q13 kw M ATTORNE Y5 INCOMING SIGNAL Aug. 22, 1961 H. H. GEORGE 2,

mcaowm: MODULATING ATTENUATOR ROLL STABILIZATION SYSTEM Filed Jan. 14. 1955 s Sheets-Sheet 3 AXIS OF RTATIO 7 CARBON COATING DIELECTRIC MATERIAL INVENTOR. If M? Y H. GEORGE BY I VERTICAL COMPONENT ATTORNEY5 United States This invention pertains generally to a stabilization system for an aerial missile, and more particularly to a roll stabilization system for a guided aerial missile which utilizes the vertical polarization of the received X-band radiation as a reference for stabilizing the missile while in aerial flight to a target.

One of the objects of this invention is to provide a system for roll stabilizing a beam riding guided missile which utilizes the vertical polarization of the received X-band radiation of the guidance beam as a reference axis.

Another object of this invention is to provide a roll stabilization system for a guided missile which utilizes a microwave modulating attenuator.

To provide an improved roll stabilization system for an aerial missile which is simple and reliable in operation, compact, and economical to manufacture, are other objects of the invention.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, and in which:

FIG. 1 is a perspective view, partly in schematic, illustrating one embodiment of the invention;

FIG. 2 is a perspective view illustrating a second embodiment of the invention;

FIG. 3 is a graph of the characteristics of the attenuator tube;

FIG. 4 is a perspective view, partly in schematic, of a roll stabilization system, incorporating the embodiment of the invention illustrated in FIG. 2;

FIG. 5 is a vector diagram representative of the input and output signals for the embodiments of the invention illustrated in FIGS. 2, 7, and 8;

FIG. 6 is a perspective, partly in cross section, of a modification of the embodiments of the invention illustrated in FIGS. 7 and 8;

FIG. 7 is a perspective view of still another embodiment of the invention;

FIG. 8 is a perspective view of still another embodiment of the invention;

FIG. 9 is an enlarged perspective view of a detail of the embodiments of the invention illustrated in FIGS. 2, 4, 7, and 8;

FIG. 10 is a section taken along line 1ll-10 of FIG. 9; and

FIG. 11 is an enlarged view of a detail of FIGS 2, 4, 7, and 8.

In accordance with the invention, there is provided a roll stabilization system for a guided aerial missile. This system comprises means including a nonpolarized antenna system having a waveguide, an attenuator means connected with the waveguide at points 90 apart, a receiver having a mixer, means for summing the outputs of the attenuator and for feeding the resultant signal to the receiver mixer, means connected with the receiver and the attenuator means for developing a roll error voltage, and means utilizing the roll error voltage to provide for roll stabilization of the missile which is caused to travel along a beam of electromagnetic energy projecting from a radar transmitter and illuminating a target.

More particularly, the electromagnetic energy is ice received by a non-polarized antenna system having two couplings to two rectangular waveguides which are oriented apart on a 45 plane. Each waveguide feeds the gas tubes of the attenuator, with the outputs therefrom being summed together in a magic tee coupled to the microwave mixer of a receiver.

The gas tubes of the attenuator have the characteristic of approximate linear attenuation to the log of the power versus bias current. A sinusoidal voltage may be applied with the bias voltage supply. This results in an average attenuation being varied sinusoidally in accordance with the applied voltage. In the circuit, the attenuator tubes are adjusted for equal average attenuation, and they are modulated equally by the applied sinusoidal signal but are difference in phase.

A modification of the above roll stabilization system is also provided to eliminate the critical attenuator gas tubes. The modified system is more adaptable to the geometry of the aerial missile. Several embodiments of the modified system are provided.

In one of the embodiments of the modified system, the nonpolarized antenna and coupling arms are mounted on the Wing tips. The two coaxial legs are coilpled to two waveguides which are placed adjacent to each other. Each waveguide has a slit in the adjacent face thereof so that an eccentrically rotated attenuator disk dips into one of the Waveguides as it is lifted out of the other waveguide. The result is that each waveguide is modulated at the rotation rate of the disk but 180 out of phase. A motor drives the disk and a rate generator to provide the reference signal for the phase sensitive rectifier as in the previous system.

Referring now to FIG. 1 of the drawings, there is illustrated a roll stabilization system for a beam riding guided missile which utilizes the vertical polarization of the received X-band radiation of the guidance beam as a reference axis for roll stabilizing a missile while in aerial flight. Energy from a guidance beam is received by a non-polarized antenna system 10 comprising a conical dielectric lens portion 12 and a cylindrical waveguide section 14. The antenna systems may be mounted in a wing tip II of a missile 13 such as illustrated in FIG. 4. It is to be noted that in this figure the antenna system has been removed from the wing tip 11 in order to better illustrate its particular features. The waveguide section 14 is coupled to two rectangular waveguides l6 and I8 oriented 90 apart on 45 planes. Waveguides 16 and 1% feed attenuator gas tubes 20 and 22, respectively. The modulated signal outputs from these tubes 20 and 22 are then passed through the wave guides 16 and 18 to a magic tee 24 where the signal outputs are summed together. The magic tee 24 is coupled to a mixer 26 comprising a local oscillator 23, a crystal detector 25, and a Waveguide section 27 of a missile receiver 28. The roll signal output from the missile receiver 28 is separated from the guidance signal by a filter 30 and then is passed to a phase comparator 32.

The attenuator tubes 20 and 22 are connected by leads 36 and 38 to two resistors 40 and 42, which, in turn, are connected through capacitors 44 and 46 to the secondary coil windings 48 of the audio-transformer 34. The center tap of the secondary winding 48 is grounded at 49. A bias voltage is applied between the resistors 40 and 42 from a bias voltage source 50. One side of the primary coil windings 52 of the audio-transformer 34 is connected to ground at 54, while the other side of the windings 52 is connected to an audio-oscillator 56, and the latter, in turn, is connected through a filter 58 to the phase comparator 32.

The attenuator gas tubes 20 and 22 have the characteristic of approximate linear attenuator to the log of the power versus bias current, as illustrated in FIG. 2. In

the system a sinusoidal voltage may be applied with the bias voltage source 50. This results in an average attenuation being varied sinusoidally in accordance with the applied voltage. In the circuit of FIG. 1, the attenuator tubes 20 and 22 have equal average attenuation and are modulated equally by the applied sine wave signal by oscillator 56 but are 180 different in phase.

Thus, for equal signals in power fed into the waveguides 16 and 18, as would be the case for the vertical axis of the aerial missile coinciding with the vertical plane of polarization of the guidance beam, no modulation appears on the signal at the receiver mixer 26 because the amount of signal increase caused by a decrease of attenuation in tube 20 is balanced by a decrease in signal by an increase in attenuation of the tube 22. Likewise, if more energy is fed in'the waveguide 16, then modulation will appear on the signal at the receiver mixer 26 of the phase of the A.C. signal applied to the attenuator tube 20. On the other hand, if more energy is fed to the waveguide 18 than to the waveguide 16, the modulation of the signal at the mixer will be 180 different in phase from that applied to the attenuator tube 22. The receiver 28 operates on this signal to derive a demodulated signal at the output of the receiver 28.

In this application, for zero degrees roll condition of the aerial missile, the vertical polarized signal from the missile guidance beam enters the non-polarized section 12 of the antenna 10. As previously indicated, since each waveguide 16 and 18 is arranged at a 45 angle, each waveguide receives one-half of the power for Zero roll condition of the missile.

However, when the missile rolls 45 clockwise, waveguide 18 receives all of the radio frequency energy and waveguide 16 receives zero radio frequency energy. The maximum AC. voltage will appear on the receiver (28) output due to the modulation of the signal by attenuator tube 22.

If the missile rolls 45 counterclockwise, the waveguide 16 will receive all of the radio frequency energy and the waveguide 18 will receive zero radio frequency energy, with the result that the maximum AC. voltage appears on the receiver output due to the modulation of the signal by attenuator tube 20 and this modulation is 180 from that of the modulation of the 45 clockwise roll mentioned above. Hence, if the applied A.C. signal and the derived A.C. signal are phase sensitive rectified, a characteristic plot of DC. volts output versus degrees roll either counterclockwise or clockwise would show a curve which passes through the origin and which is sinusoidal in shape.

Another embodiment of the waveguide system is shown in FIGS. 2 and 4 and other embodiments of waveguide systems are shown in FIGS. 7 and 8. This system of FIGS. 2 and 4 in performance is identical to the electrical system of FIGS. 1, 7 and 8, and these systems are utilized to eliminate the critical attenuator gas tubes 20 and 22. These waveguide systems are more adaptable to the geometry of an aerial missile.

In the waveguide system of FIG. 2, as well as the waveguide systems shown in FIGS. 7 and 8, the antenna lens 12, the circular waveguide 14, the local oscillator 23, the crystal detector 25, and the waveguide section '27 of the mixer are identical to the same elements shown in FIG. 1.

In the Waveguide system of FIG. 2, two waveguides 62 and 64 are located between the circular waveguide 14 and the waveguide 27 of the mixer 26. These waveguides 62 and 64 are joined to the circular waveguide 14 at a 45 angle to the vertical and are spaced 90 apart. The upper ends of the waveguides are joined to a circular waveguide 76 at a 45 angle to the vertical and are also spaced 90 apart. The center sections of the waveguides 62 and 64 are arranged parallel to each other.

Between the center sections of the waveguides 62 and 64, there is located a disk 66 of dielectric material which enters a vertical slot 70 in each waveguide 62 and 64,

with the slot 70 of waveguide 64 being shown. This disk is shown in detail in FIG. 11 and will be discussed more subsequently. This disk 66 has: eccentrically located thereon a circular coating 68 of carbon. The disk 66 is mounted for rotation on the end of a shaft 69, which is a common shaft for a motor 72 and a reference generat-or 74, which drive the shaft 69. The circular waveguide 76 is transformed to the rectangular waveguide 27, as best illustrated in FIGS. 9 and 10. This will be discussed more subsequently.

In FIGS. 7 and 8 variations of the waveguide system of FIGS. 2 and 4 are shown which incorporate the flexibility and smaller size of the microwave coaxial cables 80 and 82 for mechanical simplicity. These cables 80 and 82 are terminated by coax to waveguide terminals 84 which are mounted on the waveguides 86 and 88, in FIG. 7 and by coax to waveguide terminals 84 which are mounted on the waveguides 88 and directly on the cylin drical waveguide 14 as shown in FIG. 8. Otherwise, the performance and method of modulation for this waveguide system is identical to that previously described in FIGS. 2 and 4. r

In FIGS. 6 there is illustrated another method for deriving the two 90 separated components of microwave signal in the circular waveguide 14, as illustrated in FIGS. 1, 2, 4, 7 and 8.

In the modification of the waveguide 14, shown in FIG.

6, the center conductor 91 of the coaxial cable 80 is terthe coaxial cable 82 is terminated by a pole 9'2 which passes through the loop 90 and has its end 93 fixed to a matching stub 95. The loop 90 absorbs the horizontal component of the microwave signal from the waveguide 14, while the pole 92 absorbs the vertical component of the microwave signal from the waveguide 14. The components are then transmitted by the coaxial cables 80 and 82 to the rectangular waveguides, such as 88.

In FIGS. 9 and 10, there is illustrated the apparatus for attenuating the undesired horizontal component of the signal applied to the vertically polarized mixer crystal detector 24. The absence of this attenuation would allow the horizontal component of the microwave energy signal to be reflected back into the wave guide system to cause abnormal performance that would otherwise result in an incorrect reading of roll angle of the missile.

In FIGS. 9 and 10, there is shown the transition of the waveguide 98, from a circular section to a rectangular waveguide section 102. An attenuating material 104, such as a carbon coated dielectric, is mounted in the horizontal plane of the waveguide 98. This material 104 attenuates the undesired microwave signal, as previously mentioned.

FIG. 11 shows the modulator disk 66 used in the waveguide systems of FIGS. 2, 4, 7 and 8. This circular disk 66 is formed of dielectric material so that rotation about its center does not result in phase modulation of the microwave signals. The circular coating 68, previously mentioned is fastened to the surface of this disk 66. This coating consists of a microwave attenuating carbon material whose center is displaced from the center of the dielectric disk 66. Therefore, rotation of the dielectric disk 66 results in eccentric motion of the carbon material 68.

In FIG. 2 for zero roll angle error the signal from the A antenna 12 is divided equally in waveguides 62 and 64. As the carbon material 68 dips into the waveguide slot 70 of waveguide 62, it attenuates the microwave energy in that waveguide while, at the same time, the carbon material 68 is being removed from the slot 70 of waveguide 64 to decrease the attenuation, and, hence, to increase the signal in that waveguide. When the disk 66 is rotated by the motor 72, this results in sinusoidal amplitude modulation of the signal in waveguide 62, that is, equal but phase difference to the amplitude modulation of the signal in waveguide 64.

2 Each rotation of the disk 66 results in one cycle of sinusoidal amplitude modulation of the signals so the frequency of the modulation is the same as the revolutions per second of the motor 72. The modulated signals of waveguides 62 and 64 are summed together in the circular waveguide 76. Hence, for all practical purposes, these two equally modulated 180 out of phase signals are added together and result in zero roll error amplitude modulation of the signal applied to the mixer 26. Phase sensitive rectification of the output signal of the receiver 28, therefore, produces zero D.C. roll error voltage.

For a 45 clockwise roll error, all the microwave energy from the antenna 12 enters waveguide 64 and it is amplitude modulated by the disk 66. This energy is then passed by the circular waveguide 76 to the mixer 26. The amplitude modulation is demodulated by the receiver 28 to provide an AC. roll error voltage that is passed by the filter 30 to the phase sensitive rectifier or comparator 32. The reference voltage for the phase comparator 32 is obtained from the AC. generator 74, which is coupled by the shaft 69 to the motor 72. The output signal of the phase comparator 32 is a maximum DC. voltage signal which may, for this case, be positive in polarity.

For a 45 counter-clockwise roll error, all the energy passes down waveguide 62 to be amplitude modulated 180 phase difference from the condition mentioned in the previous paragraph. The demodulated and phase sensitive rectified signal is then a maximum negative voltage signal for this case.

FIG. 5 illustrates vectorially the separation of the two 90 components of the microwave signal in the circular waveguide 14, and their resummation in the circular waveguide 76 with this vertical component received by the crystal detector 25. The horizontal component absorbed by the attenuator of FIG. 9 is also illustrated here.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In combination, an aerial missile, a guidance system for the missile by which said missile is caused to travel along a vertically polarized beam of electromagnetic energy projected from a radar transmitter and illuminating a target, and a roll stabilization system for roll-stabilizing said missile in said beam, said roll stabilization system comprising a non-polarized antenna means including at least two waveguides located substantially ninety degrees apart for receiving the electromagnetic energy from said beam, attenuator means coupled to each Waveguide, a receiver having a mixer, means for summing together the output signals of said attenuator means and for feeding the resulting signal to the mixer of said receiver, means electrically connected to said receiver and said attenuator means for developing a roll error voltage signal, and means utilizing said roll error voltage signal to provide a control signal for roll stabilization of said missile.

2. In combination, an aerial missile, a guidance system for the missile by which said missile is caused to travel along a vertically polarized beam of electromagnetic energy projected from a radar transmitter and illuminating a target, and a roll stabilization system for roll-stabilizing said missile in said beam, said roll stabilization system comprising non-polarized antenna means including at least two waveguides located substantially ninety degrees apart, an attenuator tube coupled to each waveguide, a receiver having a mixer, means for summing together the output signals of said attenuator tubes and for feeding the resulting signal to the mixer of said receiver, means electrically connected to said receiver and said attenuator means for developing a roll error voltage signal, and means utilizing said roll error voltage signal to provide a control signal for roll stabilization of said missile.

3. In combination, an aerial missile, a guidance system for the missile by which said missile is caused to travel along a vertically polarized beam of electromagnetic energy projected from a radar transmitter and illuminating a target, and a roll stabilization system for roll-stabilizing said missile in said beam, said roll stabilization system comprising non-polarized antenna means, including at least two waveguides located substantially ninety degrees apart, attenuator means including a rotating disk having an attenuating material eccentrically mounted thereon and coupled to said waveguides, a receiver having a mixer, means for summing together the output signals of the attenuator means and for feeding the resulting signal to the mixer of said receiver, means electrically connected to said receiver and said attenuator means for developing a roll error voltage signal, and means utilizing said roll error voltage signal to provide a control signal for roll stabilization of said missile.

4. A roll stabilization system for roll-stabilizing an aerial missile in a vertically polarized guidance beam of electromagnetic energy projected from a radar transmitter and illuminating an aerial taregt, said system comprising non-polarized antenna means including at least two waveguides located substantially ninety degrees apart, attenuator means coupled to each of said waveguides, a receiver having a mixer, means for summing together the output signals of said attenuator means and for feeding the resulting signal to the mixer of said receiver, means electrically connected to said receiver and said attenuator means for developing a roll error voltage signal, and means utilizing said roll error voltage signal to provide a control signal for roll stabilization of said missile by operating a servo system, which, in turn, controls aerodynamic surfaces of said missile.

5. A roll stabilization system for roll-stabilizing an aerial missile in a vertically polarized guidance beam of electromagnetic energy projected from a radar transmitter and illuminating an aerial target, said system comprising non-polarized antenna means including at least two waveguides located substantially ninety degrees apart, an attenuator tube coupled to each of said waveguides, a receiver having a mixer, means for summing together the output signals of said attenuator tubes together and for feeding the resulting signal to the mixer of said receiver, means electrically connected to said receiver and said attenuator means for developing a roll error voltage signal, and means utilizing said roll error voltage signal to provide a control signal for roll stabilization of said missile.

6. A roll stabilization system for roll-stabilizing an aerial missile in a vertically polarized guidance beam of electromagnetic energy projected from a radar transmitter and illuminating an aerial target, said system comprising non-polarized antenna means including at least two waveguides located substantially ninety degrees apart, means including a rotating disk having an attenuating material eccentrically mounted thereon and coupled to each of said waveguides, a receiver having a mixer, means for summing together the output signals of said attenuating means and for feeding the resulting signal to the mixer of said receiver, means electrically connected to said receiver and said attenuator means for developing a roll error voltage signal, and means utilizing said roll error voltage signal to provide a control signal for roll stabilization of said missile by operating a servo system, which, in turn, controls aerodynamic surfaces of said missile.

7. A roll stabilization system for roll-stabilizing an aerial missile in a vertically polarized guidance beam of electromagnetic energy projected from a radar transmitter and illuminating an aerial target, said system comprising non-polarized antenna means including at least 7 two waveguides located substantially ninety degrees apart, attenuator means coupled to each of said waveguides, a receiver having a mixer, means for summing together the output signals of said attenuator means and for feeding the resulting signal to the mixer of said receiver, means electrically connected to said receiver and said attenuator means for developing a roll error voltage signal, means for utilizing said roll error voltage signal to provide a control signal, and means for utilizing said control signal to roll stabilize said missile.

8. A roll stabilization system for roll-stabilizing an aerial missile in a vertically polarized guidance beam of electromagnetic energy projected from a radar transmitter and illuminating an aerial target, said system comprising non-polarized antenna means including at least two waveguides located substantially ninety degrees apart, attenuator means coupled to each of said waveguides, a receiver having a mixer, means for summing together the output signals of said attenuator means and for feeding the resulting signal to the mixer of said receiver, means electrically connected to said receiver and said attenuator means for developing a roll error voltage signal, means for utilizing said roll error voltage signal to provide a control signal, and means including a servo system for utilizing said control signal to roll stabilize said missile by controlling aerodynamic surfaces of said missile. e

9. In combination with an aerial missile having an aerodynamic surface, a roll stabilization system for rollstabilizing said aerial missile in a vertically polarized guidance beam of electromagnetic energy projected from a radar transmitter and illuminating an aerial target, said system comprising non-polarized antenna means including at least two waveguides located substantially ninety degrees apart, attenuator means coupled to each of said waveguides, a receiver having a mixer, means for summing together the output signals of said attenuator means and for feeding the resulting signal to the mixer of saidreceiver, means electrically connected to said receiver and said attenuator means for developing a roll error voltage signal, means for utilizing said roll error voltage signal to provide a control signal, and means including a servo system for utilizing said control signal to roll stabilize said missile by controlling said aerody-' namic surface of said missile.

References Cited in the file of this patent UNITED STATES PATENTS 2,362,832 Land Nov. 14, 1944 

